1. Field of the Invention
The present invention is related to an improvement in anti-theft devices for liquid storage receptacles, tanks, and the like and more particularly, an anti-theft device that limits unauthorized access to a storage tank's contents without obstructing daily operations, such as product delivery, inventory control, and attendant normal activities of filling, gauging, and sampling of the tank's contents.
2. Description of the related art including information disclosed under 37 CFR Sections 1.97-1.99
Liquid storage tanks commonly have openings on their tops, some of which are quite large. These openings are normally used by authorized personnel to fill storage tanks, gauge the storage tank's contents, and sample the contents. Unfortunately, these same openings in liquid storage receptacles, tanks, hatches, or the like may also provide quick and easy access for would-be thieves to siphon the liquid contents.
An example of this type of tank opening can be found on the underground gasoline and diesel tanks currently used at many service stations. Theft of fuel product directly from an underground tank may be attempted through a fill pipe to such tanks. Traditional theft deterrents at the fill pipe, such as locking the fill cap, although of marginal success in the past, are not without attendant problems. Locks are generally considered unacceptable because keys can be lost or stolen, duplicated for use by unauthorized personnel, combinations may be difficult to keep track of and are normally forgotten, and locks tend to freeze with dirt, snow, and ice in cold weather. Further, locks external to the fill pipe may become the object of tampering or mutilation in an attempt to by-pass the same.
Anti-theft devices for use in a fill pipe for a liquid storage tank further should not obstruct daily operations relative to the tank such as product delivery and inventory control. Such normal operations routinely require tank gauging often performed with the usage of a level gauge stock to determine the volume or amount of liquid contents to the storage tank. Often, storage tank adapters or closures are designed to prevent siphoning of liquid storage tank contents while allowing for tank filling yet have no provision or ability to allow for tank gauging. Examples of such adapters or closures unable to accommodate tank gauging include U.S. Pat Nos. 1,512,065 to Taylor, 1,813,554 to Wickline, 1,933,486 to Simmonds et al., 2,006,748 to Ritz-Woller, 2,313,266 to Roberts, 2,372,545 to Breedlove, and 3,951,297 to Martin.
U.S. Pat. Nos. 1,750,849 to Malluk, 1,977,935 to Caldwell, and 1,978,313 to Lancaster are examples of art which allow tank gauging but require locks external to a fill pipe to provide tank access security.
In U.S. Pat. Nos. 1,766,916 to MacLiver and 1,862,016 to Houck there are disclosed devices capable of allowing gauging of a liquid tank without requiring locking to provide tank access security. The former patent to MacLiver discloses a gasoline theft proof device which functions as a receptacle which extends substantially to the bottom of a tank and incorporates a small opening or bleed hole to allow the receptacle liquid level to equilibrate to the tank level for gauging purposes. In the latter patent to Houck there is disclosed an automobile gasoline tank baffle which is mounted to the upper end of a neck of a tank fill pipe by threaded engagement or via three exterior screws which penetrate the fill neck and baffle. A cap is held in place by a spring clip over the open top of the tank baffle. A diametrical opening is made across the bottom wall of the baffle to allow extension of a measuring stick therethrough to gauge the contents of the storage tank.